Within an apparatus for feeding and tightening a band in a conventional strapping machine, as illustrated in FIGS. 4 (A) to (D), a touch roller 13, that is, a follower roller which rotates in subordination to and in slidable contact with a driving roller 10 of a pair of rollers 10 and 13 for grasping and feeding the band through the intermediary of a bight portion thereof is eccentrically supported on a main shaft 9 by means of an eccentric shaft 6 projecting from one end of the main shaft 9, and the main shaft 9 is caused to rotate under the influence of the tension of a spring (not shown) which is provided for biasing downwardly with respect to FIG. 4 a weight 7 inserted into one end of an adjuster 3 fixedly inserted into the other end of the main shaft 9, whereby the eccentric shaft 6 of the touch roller 13 is pivotably rotated in the form of an arc and pressed upon the driving roller 10 connected to a driving mechanism (not shown) so as to press the band therebetween and thereby provide the frictional force necessary for feeding the band.
In such a way, the band is grasped only, under the influence of the gravity of the weight 7, the fixed position of the weight 7 upon the adjuster 3, or the drag of the spring (not shown), by means of the pair of rollers 10 and 13, which are rotated forwardly in the feeding direction of the band so as to feed the band into the band guide arch upon the outside of the main body of the strapping machine. The forward rotation time adjusted by means of a timer which is set to a time slightly longer than that during which the front end of the band approaches the lower portion of a slide table 8 or a slide table switch, which senses the approach of the front end of the band, provided upon the lower portion of the slide table 8 enables the front end of the band to be transferred to a predetermined position for starting restoration of the band, this is, to a left press 47 constituting a mechanism for grasping the band feeding end below the slide table 8 or to the upper portion of a right press 40 constituting a mechanism for grasping the front end of the band; or to a time at the completion of which the front end of the band reaches and actuates a braking mechanism such as, for example, an electromagnetic brake so as to stop the rotation of the driving roller 10.
Irrespective of the fact that the band has approached the lower portion of the slide table 8 when the band is fed as described above, the braking mechanism operated by means of the signal of the timer or the signal of the slide table switch below the slide table 8, within the period of time set by the timer, permits rotation of the driving roller 10 to continue during a predetermined period of time until the actual stopping of rotation of the driving roller 10. However, the follower touch roller 13 is stopped upon the driving roller 10 which continues rotation, whereby the compressive force of the touch roller 13 upon the driving roller 10 may be adjusted by means of the weight 7 acting upon the adjuster 3, the position of the weight 7 upon the adjuster 3, or the tension of the spring (not shown) so as to cause the driving roller 10 to slip against the band.
When the band becomes jammed within the band guide arch during feeding of the band, the pair of rollers 10 and 13 cause friction upon the same portion of the band because the band does not reach the slide table switch for actuating both the band-feeding time adjusted by means of the timer and the time at which the band-feeding is stopped by means of the switch. Accordingly, the jammed band portion is scraped, locally crushed and bent, whereby the band meanders vertically or horizontally such that the band is folded within a band chute 1 having a notch within the arch portion thereof and in which portions of the circumferences of the touch roller 13 and the driving roller 10 the band is likely to be present upon the subsequent band-feeding, that is, the so-called nipping state. Even when a band jam in which the band is folded thereby forming a multilayer band, there is a situation wherein stopping of the machine and manual restoration of the band cannot resolve the folding tendency thereof.
A narrow and soft band which is susceptible to tension and is in high demand from the standpoint of costs in recent years frequently provokes difficulties such as, for example, the locking of the front end of the band within the arch because of the localized crushing, bending and the right-and-left lateral movement as well as the vertical movement thereof.
As described above, when the front end of the band approaches the lower portion of the slide table 8, a right press grasps and fixes the front end of the band so as to restore the band into the main body. When the band is restored, that is, the pair of rollers 10 and 13 or another pair of rollers are reversely rotated, the right press ascends, as shown in FIG. 4, so as to grasp the band front end. In this case, a shaft spring 44 inserted and fixed upon a press shaft 43 which rotates in synchronism with the vertical movement of the right press 40 pivotably rotates the adjuster 3 counterclockwise with respect to FIG. 4, so as to pivotably rotate the touch roller 13 so as to increase the compressive contact with the driving roller 10 and thereby enhance the compressive force developed therebetween. A spring adjuster 45 is adapted to adjust the timing at which the shaft spring 44 pivotably rotates the adjuster 3.
There is a process in which the pair of rollers reversely rotate and the band is wound around the outer periphery of an article to be strapped or another process in which the band tightly binds the article to be strapped. During these processes, a mechanism for pivotably rotating the adjuster 3 by means of the shaft spring 44 upon the press shaft 43 enhances the compressive contact force upon the driving roller 13 by means of the touch roller 10 during the reverse rotation of the pair of touch rollers. In this case, the band is restored at a predetermined time through the intermediary of the timer so as to remove the band from the band guide arch and to wind the same around the article to be strapped. A signal produced when the predetermined time of the timer is completed stops the rotation of the driving roller 10 and a tension cam 42 simultaneously rotates so as to tighten the band through means of a predetermined stroke by means of a tension arm 41. Subsequent to the generation of the aforenoted signal, that is, the completion of the band restoration, the pair of rollers 10 and 13 or another pair of rollers are rotated in a low-speed high-torque mode through the intermediary of a differential speed-reducing mechanism, whereby the band is more firmly tightened and bound around the article to be strapped. The reverse rotation time set by means of the timer is adequately adjusted according to the expected minimum dimensions of the article to be strapped. The period comprising the predetermined time of the timer established by estimating the time of completion of restoration of the band, which is removed from the band guide of the band guide arch or from a freely opening and closing flap, to be wound around the article to be strapped, even when the band is wound around the article to be strapped, does not always start the tightening process in which the tension arm 41 or the pair of rollers 10 and 13 or another pair of rollers rotate in a low-speed high-torque mode through means of the intermediary of a differential speed-reducing mechanism, thereby resulting in considerable time loss for high-speed strapping in which as little as 1/10 second becomes a matter of concern. As described above, even if the band is wound around the article to be strapped a braking mechanism such as, for example, an electromagnetic brake is actuated within the period of time set by means of the timer or because of the generated signal of the timer so as to permit the rotation of the driving roller 10 to continue for a very short period of time until the rotation of the driving roller 10 is stopped. The shaft spring 44 is so adjusted that the follower touch roller 13 stops upon the driving roller 10 which continues rotation and the driving roller 10 then slips against the band. Accordingly, the pair of rollers 10 and 13 may, as is the case with the above described band-feeding, scratch the identical portion of the band, which is scraped, locally crushed, folded, and then moves in a right-and-left lateral direction as well as vertically, resulting of the band within folding-up in the band chute 1 and so-called nipping thereof so as to form a jam of the band. In this case, the folded or crushed band portion must be cut and thrown away.